Countries that have defaulted since 1975 had non-investment credit rating grades (below BBB) a year before they defaulted, the IMF found in 2010, but that doesn’t mean rating agencies reveal anything markets don’t already know.

Far from raising doubts about the U.K.’s creditworthiness, investors have continued to lap up gilts in the wake of S&P’s decision to cut its sovereign rating for the U.K. two notches to AA. Yields on the U.K. government’s 10-year bonds are still hugging 0.95% in the wake of S&P’s announcement, below the historic 1% threshold breached for the first time last week.

In other words, rating changes appear to follow -- rather than lead -- market moves.

Credit-default swap prices on U.K. bonds, the market’s best estimate of the probability of default, had incorporated the impact of Brexit even before rival rating agency Moody’s -- which had already withdrawn its top rating -- put the U.K. on ‘negative watch’ on Friday. Two notches is quite a rebuke, too, not to mention competitor Fitch cut its credit score for the U.K. on the same day.

France, arguably in perennially worse fiscal shape than Britain, had its credit rating shaved to AA+ in January 2012, before enduring a trim to AA in November 2013. Credit-default swap spreads on French debt edged up a mere basis point on that day to around 50.

Perhaps the biggest sign of a relevance deficit came in August 2011, when S&P stripped the U.S. government of its AAA rating amidst heightened risk Congress would refuse to lift the debt ceiling. Yields on U.S. government bonds actually fell in following days, by around 20 basis points. And remarkably, U.S. government CDS spreads flat-lined.

S&P even stuck an A+ badge on debt-laden Japan’s debt last September, but yields on Tokyo’s bonds recently sank below zero. Australia and Canada, meanwhile, boasting far higher AAA credit ratings from S&P, have to pay well over 1% to borrow.

Should S&P, Moody’s, and the others abandon their practice of giving governments unsolicited ratings?

Rating change for states might be great free advertising, but superfluity isn’t typically a good corporate look, especially when a host of regulators and experts want to curb agencies’ already diminished role in financial regulation.

Rating governments is inherently more difficult than rating private firms. Most governments can choose to print their own money to repay debts, as Germany famously did almost a century ago, or sell real assets to raise foreign currency. And agencies have no greater insight into a government’s propensity to fulfill its obligations beyond analysis of its publicly available financial and economic statistics, which actual creditors have a stronger incentive to pore over.

S&P said the U.K.’s Brexit vote would lead to “less predictable, stable, and effective” policies, prompt constitutional issues with Scotland, and potentially undermine sterling’s place as a reserve currency. These are hardly revelations.

Sovereign ratings have been steadily dwindling since the financial crisis: Ireland, Spain, Italy, Finland have all been downgraded too, accompanied by similar whimpers on financial markets. Corporate credit quality has been following suit: Johnson & Johnson and Microsoft are the only firms left in the corporate AAA club after Exxon was downgraded in April.

An unforeseen burst of deflation may yet put the agencies’ pessimism in better light – perhaps real borrowing costs are rising even if nominal costs are falling. But on the issue of national creditworthiness, they seem to have little new to add for now.